Accounting for soil architecture and microbial dynamics in microscale models: Current practices in soil science and the path ahead

Macroscopic models of soil organic matter (SOM) turnover have faced difficulties in reproducing SOM dynamics or in predicting the spatial distribution of carbon stocks. These models are based on a largely inadequate linear response of soil microorganisms to bulk concentrations of nutrients and it is clear that a new approach to SOM modelling is required. Introducing explicit microbial activity and organic matter (OM) reactivity in macroscopic models represents a challenge because of the fine spatial scales at which the processes occur. To get a better grasp on interactions that take place at the microscale, a new generation of SOM models have been developed at the spatial scale of the soil microenvironments where microorganisms evolve. These models are well adapted to challenge traditional hypotheses about the influence of soil architecture on soil microbial activity. Soil architecture provides the stage for a dynamic spatial accessibility of resources to microbes and the emergence of interactions between the actors in SOM decomposition. In this context, we review microscale models of microbial activity that have been designed for soils and soil analogues. To understand how these models account for spatial accessibility, we look in detail at how soil microenvironments are described in the different approaches and how microbial colonies are spatialized in these microenvironments. We present the advantages and disadvantages of the developed strategies and we discuss their limits. Highlights We review the state of the art in the development of microscale models of soil microbial processes. Microscale models have integrated the tremendous progress in knowledge of OM cycling in soils. We categorize modelling approaches by how they deal with complexity of soil architecture. Modelling benchmarks are required to properly balance complexity and data uncertainty.

Automated summary

The development of new generation soil organic matter (SOM) models at the spatial scale of soil microenvironments challenges traditional hypotheses about influences on soil microbial activity. These models better capture interactions at the microscale and provide insights into the dynamics of SOM decomposition.